Method for producing purified dialkyl-furan-2,5-dicarboxylate

ABSTRACT

Disclosed is a purified dialkyl furan dicarboxylate (DAFD) vapor composition containing at least 99.5 wt. % DAFD; 5-(alkoxycarbonyl) furan-2-carboxylic acid (ACFC) that, if present, is present in an amount of not more than 1000 ppm, alkyl-5-formylfuran-2-carboxylate (AFFC) that, if present, is present in an amount of not more than 1000 ppm, 5-(dialkoxymethyl)furan-2-carboxylic acid (DAFCA) that if present, is present in an amount of not more than 1000 ppm, and alkyl 5-(dialkoxymethyl)furan-2-carboxylate (ADAFC) that if present, is present in an amount of not more than 1000 ppm, in each case based on the weight of the DAFD vapor composition.

1. CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 15/875,352filed on Jan. 19, 2018, which claims the benefit of ProvisionalApplication No. 62/534,897, filed Jul. 20, 2017, the disclosure of whichis incorporated herein by reference in its entirety.

2. FIELD OF THE INVENTION

The invention relates to the processes for the production of purifieddialkyl-furan-2,5-dicarboxylate (DAFD) vapor and purified DAFDcompositions made therefrom.

3. BACKGROUND OF THE INVENTION

Aromatic dicarboxylic acids such as terephthalic acid and isophthalicacid or their di-esters, dimethyl terephthalate as for example, are usedto produce a variety of polyester products, important examples of whichare poly (ethylene terephthalate) and its copolymers. The aromaticdicarboxylic acids are synthesized by the catalytic oxidation of thecorresponding dialkyl aromatic compounds which are obtained from fossilfuels such as those disclosed in US 2006/0205977 A1. Esterification ofthese diacids using excess alcohol produces the corresponding di-estershas been disclosed in US2010/0210867A1. There is a growing interest inthe use of renewable resources as feed stocks for the chemicalindustries mainly due to the progressive reduction of fossil reservesand their related environmental impacts.

Furan-2,5-dicarboxylic acid (“FDCA”) is a versatile intermediateconsidered as a promising closest biobased alternative to terephthalicacid and isophthalic acid. Like aromatic diacids, FDCA can be condensedwith diols such as ethylene glycol to make polyester resins similar topolyethylene terephthalate (PET) as disclosed in Gandini, A.; Silvestre,A. J; Neto, C. P.; Sousa, A. F.; Gomes, M. J. Poly. Sci. A 2009, 47,295. FDCA has been prepared by oxidation of 5-(hydroxymethyl) furfural(5-HMF) under air using homogenous catalysts as disclosed inUS2003/0055271 A1 and in Partenheimer, W.; Grushin, V. V. Adv. Synth.Catal. 2001, 343, 102-111. However, achieving high yields has proveddifficult. A maximum of 44.8% yield using Co/Mn/Br catalysts system anda maximum of 60.9% yield was reported using Co/Mn/Br/Zr catalystscombination.

The crude FDCA obtained by the oxidation processes must to be purifiedbefore they are suitable for end-use applications. JP patentapplication, JP209-242312A, disclosed crude FDCA purification processusing sodium hydroxide/sodium hypochlorite and/or hydrogen peroxidefollowed by acid treatment of the disodium salt to obtain pure FDCA.This multi-step purification process generates wasteful by-products.

Therefore, there is a need for an inexpensive and high yield process forthe purification of crude FDCA that minimizes the creation of additionalwaste products and lends itself to efficient separation step(s).

4. SUMMARY OF THE INVENTION

There is now provided a process for the manufacture of DAFD vaporcomprising:

-   -   a. feeding a furan-2,5-dicarboxylic acid (“FDCA”) composition to        an esterification reaction zone; and    -   b. in the presence of an alcohol compound, conducting an        esterification reaction in the esterification reaction zone to        react FDCA with said alcohol compound to form a crude diester        composition comprising dialkyl furan-2,5-dicarboxylate (“DAFD”),        the alcohol compound, 5-(alkoxycarbonyl)furan-2-carboxylic acid        (ACFC), alkyl furan-2-carboxylate (AFC),        alkyl-5-formylfuran-2-carboxylate (AFFC),        5-(dialkoxymethyl)furan-2-carboxylic acid (DAFCA) and alkyl        5-(dialkoxymethyl)furan-2-carboxylate (ADAFC), and    -   c. separating at least a portion of the alcohol compound from        the crude diester composition in a flash zone using a physical        separation process to produce:        -   (i) a vapor alcohol composition, comprising said alcohol            compound, taken as an overhead stream that is rich in the            concentration of alcohol, relative to the alcohol            concentration in the crude diester composition feeding the            flash zone, and        -   (ii) a first liquid DAFD rich composition, comprising DAFD,            ACFC, AFC, AFFC, DAFCA, and ADAFC that is rich in the total            concentration of DAFD relative to the total concentration of            DAFD in the crude diester composition feeding the flash            zone; and    -   d. separating at least a portion of DAFD from the first liquid        DAFD rich composition in a product recovery zone;    -   wherein the process produces a composition comprising:        -   (i) at least 99.5 wt. % DAFD;        -   (ii) 5-(alkoxycarbonyl)furan-2-carboxylic acid (ACFC) that            if present, is present in an amount of not more than 1000            ppm,        -   (iii) alkyl-5-formylfuran-2-carboxylate (AFFC) that if            present, is present in an amount of not more than 1000 ppm        -   (iv) 5-(dialkoxymethyl)furan-2-carboxylic acid (DAFCA) that            if present, is present in an amount of not more than 1000            ppm, and        -   (v) alkyl 5-(dialkoxymethyl)furan-2-carboxylate (ADAFC) that            if present, is present in an amount of not more than 1000            ppm,    -   in each case based on the weight of the DAFD vapor composition.        -   There is also provided a purified dialkyl furan            dicarboxylate (DAFD) vapor composition comprising:        -   (i) at least 99.5 wt. % DAFD;        -   (ii) 5-(alkoxycarbonyl)furan-2-carboxylic acid (ACFC) that            if present, is present in an amount of not more than 1000            ppm,        -   (iii) alkyl-5-formylfuran-2-carboxylate (AFFC) that if            present, is present in an amount of not more than 1000 ppm        -   (iv) 5-(dialkoxymethyl)furan-2-carboxylic acid (DAFCA) that            if present, is present in an amount of not more than 1000            ppm, and        -   (v) alkyl 5-(dialkoxymethyl)furan-2-carboxylate (ADAFC) that            if present, is present in an amount of not more than 1000            ppm,    -   in each case based on the weight of the DAFD vapor composition.        -   There is also provided a purified liquid DAFD composition            comprising:        -   (i) at least 99.9 wt. % DAFD;        -   (ii) not more than 100 ppm ACFC,        -   (iii) not more than 100 ppm AFFC,        -   (iv) not more than 10 ppm furan dicarboxylic acid (FDCA),        -   (v) not more than 100 ppm DAFCA, and        -   (vi) not more than 100 ppm ADAFC,    -   in each case based on the weight of the DAFD vapor composition.        -   There is also provided a solids DAFD composition comprising            solid particles of DAFD, wherein said solids comprise:        -   (i) at least 99.5 wt. % liquid DAFD;        -   (ii) 5-(alkoxycarbonyl)furan-2-carboxylic acid (ACFC) that            if present, is present in an amount of not more than 1000            ppm,        -   (iii) alkyl-5-formylfuran-2-carboxylate (AFFC) that if            present, is present in an amount of not more than 1000 ppm,        -   (iv) 5-(dialkoxymethyl)furan-2-carboxylic acid (DAFCA) that            if present, is present in an amount of not more than 1000            ppm,        -   (v) alkyl 5-(dialkoxymethyl)furan-2-carboxylate (ADAFC) that            if present, is present in an amount of not more than 1000            ppm,        -   (vi) not more than 1 wt. % water, and        -   (vii) not more than 1 wt. % solids,    -   in each case based on the weight of the purified liquid DAFD        composition.

5. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of the process for making both FDCA andpurified DAFD.

FIG. 2 is a flow diagram illustrating a feed of raw materials to amixing zone prior to feeding the slurry to an esterification reactor.

FIG. 3 is a flow diagram depicting the process of producing a purifiedDAFD vapor composition using a combination of separation zones.

6. DETAILED DESCRIPTION OF THE INVENTION

It should be understood that the following is not intended to be anexclusive list of defined terms. Other definitions may be provided inthe foregoing description, such as, for example, when accompanying theuse of a defined term in context.

As used herein, the terms “a,” “an,” and “the” mean one or more.

As used herein, the terms “comprising,” “comprises,” and “comprise” areopen-ended transition terms used to transition from a subject recitedbefore the term to one or more elements recited after the term, wherethe element or elements listed after the transition term are notnecessarily the only elements that make up the subject.

As used herein, the terms “containing,” “having,” “has,” and “have” havethe same open-ended meaning as “comprising,” “comprises,” and “comprise”provided above.

As used herein, the terms “including,” “includes,” and “include” havethe same open-ended meaning as “comprising,” “comprises,” and “comprise”provided above.

The present description uses numerical ranges to quantify certainparameters relating to the invention. It should be understood that whennumerical ranges are provided, such ranges are to be construed asproviding literal support for claim limitations that only recite thelower value of the range as well as claim limitations that only recitethe upper value of the range. For example, a disclosed numerical rangeof 10 to 100 provides literal support for a claim reciting “greater than10” (with no upper bounds) and a claim reciting “less than 100” (with nolower bounds).

The present description uses specific numerical values to quantifycertain parameters relating to the invention, where the specificnumerical values are not expressly part of a numerical range. It shouldbe understood that each specific numerical value provided herein is tobe construed as providing literal support for a broad, intermediate, andnarrow range. The broad range associated with each specific numericalvalue is the numerical value plus and minus 60 percent of the numericalvalue, rounded to two significant digits. The intermediate rangeassociated with each specific numerical value is the numerical valueplus and minus 30 percent of the numerical value, rounded to twosignificant digits. The narrow range associated with each specificnumerical value is the numerical value plus and minus 15 percent of thenumerical value, rounded to two significant digits. For example, if thespecification describes a specific temperature of 62° F., such adescription provides literal support for a broad numerical range of 25°F. to 99° F. (62° F.+/−37° F.), an intermediate numerical range of 43°F. to 81° F. (62° F.+/−19° F.), and a narrow numerical range of 53° F.to 71° F. (62° F.+/−9° F.). These broad, intermediate, and narrownumerical ranges should be applied not only to the specific values, butshould also be applied to differences between these specific values.Thus, if the specification describes a first pressure of 110 psia and asecond pressure of 48 psia (a difference of 62 psia), the broad,intermediate, and narrow ranges for the pressure difference betweenthese two streams would be 25 psia to 99 psia, 43 psia to 81 psia, and53 psia to 71 psia, respectively.

The word “rich” in reference to a composition means the concentration ofthe referenced ingredient in the composition is higher than theconcentration of the same ingredient in the feed composition to theseparation zone by weight. For example, a liquid DAFD rich compositionmeans that the concentration of DAFD in the liquid DAFD rich compositionis greater than the concentration of DAFD in the stream feeding theseparation zone, in this case, the crude diester composition.

All amounts are by weight unless otherwise specified. All references toppm are on a mass basis.

As illustrated in FIG. 1 , a dicarboxylic acid composition stream 410,which can be either dried carboxylic acid solids or a wet cakecontaining carboxylic acid, in each case the carboxylic acid comprisingfuran dicarboxylic acid (“FDCA”), and an alcohol composition stream 520are fed to the esterification reaction zone 500. The solid dicarboxylicacid composition 410 can be shipped via truck, ship, or rail as solidsto a plant or facility for the manufacture of the diester composition.The process for the oxidation of the oxidizable material containing thefuran group can be integrated with the process for the manufacture ofthe diester composition. An integrated process includes co-locating thetwo manufacturing facilities, one for oxidation and the other foresterification, within 10 miles, or within 5 miles, or within 2 miles,or within 1 mile, or within ½ mile of each other. An integrated processalso includes having the two manufacturing facilities in solid or fluidcommunication with each other. If a solid dicarboxylic acid compositionis produced, the solids can be conveyed by any suitable means, such asair or belt, to the esterification facility. If a wet cake dicarboxylicacid composition is produced, the wet cake can be moved by belt orpumped as a liquid slurry to the facility for esterification.

The esterification zone 500 comprises at least one esterificationreactor. The dicarboxylic acid composition comprising FDCA is fed to theesterification zone and, in the presence of an alcohol compound, anesterification reaction is conducted in the esterification reaction zoneto react FDCA with said alcohol compound to form a crude diestercomposition comprising dialkyl furan-2,5-dicarboxylate (“DAFD”), thealcohol compound, 5-(alkoxycarbonyl)furan-2-carboxylic acid (ACFC),alkyl furan-2-carboxylate (AFC), and alkyl-5-formylfuran-2-carboxylate(AFFC). The crude diester composition may optionally contain a catalystif a homogeneous esterification catalyst is used.

The alcohol composition comprises one or more types of alcoholcompounds. Examples include compounds represented by the structure R—OHwherein R can range from 1 to 6 carbons, or 1 to 5 carbon atoms, or 1 to4 carbon atoms, or 1 to 3 carbon atoms, or 1 to 2 carbon atoms,preferably methanol. R can be branched or unbranched, saturated orunsaturated, and cyclic or acyclic. Desirably, R is an unbranched,saturated, acyclic alkyl group. The alcohol composition contains atleast 50 wt. %, or at least 60 wt %, or at least 70 wt %, or at least 80wt. %, or at least 90 wt. %, or at least 95 wt %, or at least 97 wt %,or at least 98 wt. %, or at least 99 wt. % alcohol compounds based onthe weight of the alcohol composition. Desirably, the alcoholcomposition comprises methanol.

The crude diester composition produced in the esterification zone 500 isthe reaction product of at least FDCA with the alcohol composition toproduce DAFD, where the alkyl moiety is an alkyl group containing 1 to 6carbon atoms, and at least a portion of the alkyl moiety corresponds tothe alcohol residue. In the case of a reaction between FDCA andmethanol, the diester reaction product comprises dimethylfuran-2,5-dicarboxylate (“DMFD”). The esterification reaction of FDCAwith methanol to produce DMFD comprises multiple reaction mechanisms asillustrated below. One reaction mechanism comprises reacting one mole ofFDCA with one mole of Methanol to produce a mole of5-(methoxycarbonyl)furan-2-carboxylic acid (MCFC) and water. One mole ofMCFC can then react with one mole of methanol to produce one mole of thedesired product DMFD and water. Because both DMFD and MCFC are presentin an esterification reaction zone, the crude diester composition willalso contain MCFC in addition to the unreacted hydroxyl compounds andDMFD. A commercial process to produce purified DMFD must allow for theseparation of DMFD and MCFC downstream of the esterification zone.

Esterification by-products are also formed in reaction zone 500 andcomprise chemicals with boiling points both higher and lower than DMFD.Esterification by-products formed in the esterification reaction zonecomprise methyl acetate, alkyl furan-2-carboxylate (AFC), alkyl5-formylfuran-2-carboxylate (AFFC), and5-(alkoxycarbonyl)furan-2-carboxylic acid (ACFC). Many other by-productsare possible depending upon the impurities contained within the FDCAfeedstock. One of the major by products in the crude FDCA that can formimpurities during esterification is FFCA. FFCA can react with thealcohol to form 5-(dialkoxymethyl)furan-2-carboxylic acid (DAFCA) andalkyl 5-(dialkoxymethyl)furan-2-carboxylate (ADAFC) impurities:

When methanol is used as an esterification alcohol, its reaction withFFCA impurity in the crude FDCA can generate5-(dimethoxymethyl)furan-2-carboxylic acid (DMFCA) and methyl5-(dimethoxymethyl)furan-2-carboxylate (MDMFC):

A commercial process to produce a purified DAFD stream must allow forthe separation of impurities from the crude di-ester composition exitingas stream 510. Further, at least a portion of these impurities can bepurged from the process wherein purging involves isolation of theimpurities and routing them from the process.

It is desirable to first mix the FDCA composition with the alcohol priorto conducting an esterification reaction under esterificationconditions. As illustrated in FIG. 2 , there is provided a mixing zone540 and esterification reactor 550 within the esterification zone 500.The dicarboxylic acid composition 410 comprising FDCA, an alcoholcomposition 520, optionally an esterification catalyst system 530, andoptionally an alcohol recycle stream 802 comprising a recycled alcoholat least one of which is the same type of compounds as fed in stream 520are mixed in the mixing zone 540 to generate mixed reactor feed stream501. In one embodiment, streams 520 and 802 comprise methanol.

Mixing in zone 540 may be accomplished by any equipment known in the artfor mixing liquid and solids, such as continuous in line static mixers,batch agitated vessels, and or continuous agitated vessels, and thelike. The theoretical amount of alcohol required for the reaction witheach mole of FDCA in the esterification zone, or the esterificationreactor 550, or in the mixing zone 540, is two moles. The total amountof alcohol present in mixing zone 540 is desirably in excess of thetheoretical amount required for the esterification reaction.

For example, the molar ratio of alcohol to FDCA moles ranges fromgreater than 2:1, or at least 2.2:1, or at least 2.5:1, or at least 3:1,or at least 4:1, or at least 8:1, or at least 10:1, or at least 15:1, orat least 20:1, or at least 25:1, or at least 30:1 and can go as high as40:1. Suitable molar ratios are within a range of alcohol to FDCA from10:1 to 30:1.

To the mixing zone 540 may also be fed an esterification catalyst systemas stream 530 if a catalyst is used. The catalyst is can beheterogeneous or desirably a homogenous catalyst under esterificationreaction conditions, and can also be homogeneous in the mixing zone.Known organometallic esterification catalysts can be used such as theacetate or other carboxylate or glycolate of cobalt, copper andmanganese, cadmium, lead, lithium, and zinc in amounts conventionallyused for esterifying terephathalic acid. Other organic catalysts can beemployed such as sulfuric acid, tosylic acid, and Lewis acids.

The mixed reactor feed stream 501 is routed to esterification reactor550 to generate a crude diester composition discharged from theesterification reactor 550 as liquid crude diester stream 510. The crudediester composition 510 discharged from the esterification zone 500desirably contains DAFD present in an amount of at least 5 wt %, or atleast 8 wt. %, or at least 10 wt. %, or at least 15 wt. %, or at least20 wt. %, and up to 40 wt. %, or up to 35 wt. %, based on the weight ofthe whole crude diester composition, and desirably in each case based onthe weight of the liquid phase. At the high temperatures, high pressure,and/or high alcohol concentration under esterification conditions, theDAFD present in the crude diester composition is solubilized and thesolids concentration is generally not more than 5 wt. %, or not morethan 2 wt. %, or not more than 1 wt. %, or not more than 0.5 wt. %, ornot more than 0.1 wt. %, although the amount of solids can be higher asthe concentration of unreacted alcohol is diminished and the reactiontemperature is reduced. If solids are present, at least 95 wt. %, or atleast 96 wt. %, or at least 97 wt. %, or at least 98 wt. %, or at least99 wt. % of the solids are unreacted FDCA solids.

The yield of DAFD in the crude diester composition desirably high.Suitable yields are at least 55 mole %, or at least 60 mole %, or atleast 65%, or at least 70 mole %, or at least 75 mole %, or at least 80mole %, or at least 85 mole %, or at least 90 mole %, or at least 95mole %, or at least 99 mole %. The yield of DAFD in the crude diesterstream is calculated as follows:(mol of DAFD in the crude diester composition in the liquidphase/starting mol of FDCA)*100%.

The crude FDCA slurry stream can be fed into the esterification reactorat a rate corresponding to a desired throughput in a continuous processfor the production of a purified DAFD vapor composition. Examples ofsuitable rates for the production of a purified DAFD vapor compositionstream include an average of at least 1000 kg/day, or at least 10,000kg/day, or at least 20,000 kg/day, or at least 50,000 kg/day, or atleast 75,000 kg/day, or at least 100,000 kg/day, or at least 200,000kg/day of a purified DAFD vapor composition, on a 24 hour basis over thecourse of any three months.

Esterification may be accomplished in batch or continuous reactors andcomprises one or multiple reaction vessels that are capable of providingacceptable reaction residence time, temperature, and pressure. Theesterification reaction residence time ranges from 0.5 hr to about 10hours. The esterification temperature ranges from 150° C. to below thesupercritical temperature of the alcohol selected to ensure that thealcohol stays in liquid phase at reaction pressures. Suitable reactiontemperatures can range from 150° C. to 250° C., or 150° C. to 240° C.,or from 200° C. to 230° C. Particularly suitable is an upper range of240° C. in the case methanol is used as the alcohol. The esterificationpressure within the esterification reactor is sufficient to maintain thealcohol compound in the liquid phase and will vary with the temperatureselected. Suitable pressure ranges are from about 250 psig to about 2000psig, or from 400 psig to 1500 about psig.

The crude diester composition is taken from the esterification reactorin the esterification zone 500 in a stream 510 and fed to a flash zone600 as shown in FIG. 1 . At least a portion of alcohol compound in thecrude diester composition is separated from the crude diester stream inthe flash zone 600 in a physical separation process to produce a firstliquid DAFD rich composition stream 620 containing liquid DAFD, and inwhich the concentration of DAFD in the DAFD rich composition is higherthan the concentration of DAFD in the crude diester composition feedingthe flash zone 600. In the flash zone, the crude diester compositionexperiences a pressure letdown to flash alcohol resulting also inevaporative cooling.

The crude diester composition exits the esterification zone 500 atelevated temperatures, typically at a temperature of at least 150° C.,or at least 170° C., or at least 180° C., or at least 190° C., or atleast 200° C., or at least 210° C., or at least 220° C., or at least230° C., or at least 240° C., and in each case below the supercriticaltemperature of the alcohol. To take advantage of the sensible heatenergy already present in crude diester composition, one may simplyconduct the physical separation under a pressure that is lower relativeto the pressure over the crude diester stream upon entry into theseparation zone, and thereby take off alcohol through reduced pressureto produce a first liquid DAFD rich composition as stream 620. This canbe accomplished without applying heat energy to the separation vesselfor separation purposes to thereby reduce energy consumption (e.g.adiabatic flash).

The flash zone 600 can comprise one or more vessels for flash separationthrough pressure reduction operated in series or parallel withoutapplication of external heat energy to effect the separation. Forexample, the flash zone 600 can comprise one or more evaporative flashunit operations, or can comprise one or more distillation columns. Thealcohol separation zone can comprise both a flash evaporation unit and adistillation column. The separation zone may be operated in a batch orcontinuous mode.

Desirably, the flash zone 600 contains at least a flash evaporation unitsuch as a flash tank. One may conduct staged flash evaporation inmultiple vessels. The pressure in the flash unit operation can rangefrom 0 psig to about 150 psig, or from 0 psig to about 50 psig, or from0 psig to 35 psig. If alcohol is separated under a reduced pressurerelative to the pressure of the crude diester composition at the entryto the physical separation vessel, it is desirable that the pressurewithin the flash vessel is below the vapor pressure of the alcohol atthe temperature of the crude diester stream at the entry port to theflash vessel.

The temperature of the first liquid DAFD rich composition stream 620discharged from the flash zone 600 is not particularly limited. It willbe lower than the temperature of the crude diester stream entering theflash zone due to evaporative cooling. In one embodiment, thetemperature of the first liquid DAFD rich composition stream 620 is atleast 5° C. cooler, or at least 20° C. cooler, or at least 50° C.cooler, or at least 75° C. cooler, or at least 100° C. cooler, or atleast 120° C. cooler than the crude diester composition temperatureentering the flash zone 600. One may employ a series of flash vesselsthat have small incremental temperature drops such that the cumulativetemperature drop of all the vessels within the zone add up to at leastthese stated values.

A vapor alcohol composition stream 610 is generated in the flash zone600. The vapor alcohol composition stream 610 comprises alcohol, somewater, and optionally a small (e.g. less than 0.1 wt %) DAFD can also bepresent. The vapor alcohol composition stream 610 is rich in theconcentration of alcohol, relative to the alcohol concentration in thecrude diester composition 510. Desirably, the concentration of alcoholin the vapor alcohol composition 610 comprises at least 70 wt. %alcohol, or at least 80 wt. % alcohol, or at least 90 wt. %, or at least95 wt. % alcohol.

The vapor alcohol composition stream 610 is fed to an alcohol recoveryzone 800. The alcohol recovery zone generates a purified alcohol stream802 comprising alcohol that is depleted in the concentration of wateralcohol relative to the concentration of water in the vapor alcoholcomposition stream 610, and generates a water stream 801 that is rich inthe concentration of water relative to the concentration of water in thevapor alcohol stream 610.

The alcohol recovery zone 800 can comprise one or more distillationcolumns to effect the separation of alcohol from water. The distillationcolumn can be dedicated to receive a feed of the vapor alcoholcomposition 610 or the vapor alcohol composition 610 can be firstcondensed and fed to the distillation column. The purified alcoholcomposition 802 may be one or more vapor distillates and if desired, atleast a portion can be condensed and at least a portion can be fed as arecycle stream back to the esterification zone 500.

Alternatively, the vapor alcohol composition gaseous overhead stream610, or liquid if condensed, can be fed to a shared distillation columnin alcohol recovery zone 800 that also receives a feed of a secondalcohol rich stream 712. It is desired to use a shared distillationapparatus to reduce capital costs.

The first liquid DAFD rich composition stream 620 comprises DAFD rich (ahigher concentration) in the concentration of DAFD relative to theconcentration of DAFD present in the crude diester stream 510 exitingthe esterification zone 500. The concentration of DAFD in the DAFD richstream can be increased by at or at least 20%, or at least 30%, or atleast 40%, or at least 50%, or at least 70%, or at least 90%, or atleast 100%, or at least 150%, or at least 200%, or at least 250%, or atleast 300%, or at least 400%, or at least 500%, over the concentrationof DAFD in the crude diester composition 510. The DAFD rich streamdesirably contains DAFD present in an amount of at least 5 wt. %, or atleast 10 wt %, or at least 20 wt %, or at least 30 wt %, or at least 40wt %, or at least 50 wt %, or at least 60 wt %, and in each case up to70 wt. %, or up to 80 wt %, in each case based on the weight of the DAFDrich composition.

The first liquid DAFD rich stream desirably contains no solids. Ifpresent, the solids comprise DAFD and/or unreacted FDCA or otherby-products reacting with DAFD and/or FDCA. The solids concentration inthe DAFD composition may contain no more than 55 wt. %, or up to 45 wt.%, or up to 35 wt. %, or up to 28 wt. %, or up to 15 wt. %, or up to 10wt. %, or up to 5 wt. %, or up to 3 wt. %, or up to 2 wt. %, and ifpresent, an amount of greater than zero, each based on the weight of thefirst liquid DAFD rich composition 620.

The first liquid DAFD rich composition stream 620 also contains anyalcohol that did not separate in the flash zone 600, some water, and aquantity of some or all of the by-products mentioned above. The amountof alcohol in the first liquid DAFD rich stream is greater than zero, orat least 1 wt. %, or at least 2 wt. %, or at least 3 wt. %, or at least5 wt. %, or at least 10 wt. %, or at least 15 wt. %, and up to 60 wt. %,or up to 50 wt. %, or up to 40 wt. %, based on the weight of the DAFDrich stream.

As shown in FIG. 1 , the first liquid DAFD rich composition stream 620is fed to a product recovery zone 700 to separate at least a portion ofDAFD from the first liquid DAFD rich composition in the product recoveryzone using one or more physical separation processes to produce:

-   -   (i) a purified DAFD vapor composition rich in the concentration        of DAFD relative to the concentration of DAFD in the first        liquid DAFD rich composition; and    -   (ii) a liquid ACFC composition that is rich in the concentration        of ACFC relative to the concentration of ACFC in the first        liquid DAFD rich composition; and    -   (iii) a vapor AFC composition comprising AFC that is rich in the        concentration of AFC relative to the concentration of AFC in the        first liquid DAFD rich composition; and    -   (iv) a second vapor alcohol composition, comprising alcohol,        that is rich in the concentration of alcohol, relative to the        first liquid DAFD rich composition.

The product recovery zone 700 may contain one or more distillationcolumns to effect one or more separations.

As an example, the product recovery zone 700 may contain analcohol-water removal zone 710, as shown in FIG. 3 , comprising aphysical separation unit to separate alcohol from the first liquid DAFDrich composition, thereby producing a second alcohol composition stream712 discharged from the top of the column that is rich in theconcentration of alcohol relative to the concentration of alcohol in thefirst liquid DAFD rich composition stream 620, and a second liquid DAFDrich composition stream 711 comprising DAFD that is rich in theconcentration of DAFD relative to the concentration of DAFD in the firstliquid DAFD rich composition stream 620. Desirably the concentration ofalcohol in the second liquid DAFD rich composition is depleted (orlower) relative to the concentration of alcohol in the first liquid DAFDrich composition. Also, desirably the concentration of DAFD in thesecond alcohol composition stream 712 discharged from the top of thecolumn is depleted relative to the concentration of DAFD in the secondliquid DAFD rich composition stream 711.

An example of a suitable devices for carrying out the separation ofalcohol from the first liquid DAFD rich composition stream 620 is anytype of distillation column (tray or packed).

The second alcohol composition stream 712 can, if desired, be feddirectly to the alcohol recovery zone 800 as a vapor to separate waterfrom the second alcohol composition stream 712. Alternatively, thesecond alcohol composition stream 712 can, if desired, be condensed,with a portion of the condensed alcohol composition fed back to thecolumn as reflux and a portion of the condensed alcohol composition fedto the alcohol recovery zone 800 as a liquid. Thus, stream 712 fed tothe alcohol recovery zone 800 is either a liquid and/or a vapor. Thealcohol recovery zone 800 separates alcohol from the second alcoholcomposition stream 712. The alcohol recovery zone 800 can also be usedto accept a feed of the first vapor alcohol composition stream 610 toseparate alcohol from the first vapor alcohol composition stream 610,and the same distillation column can be used to accept feeds 610 and712. Alternatively, a second distillation column can be used to acceptfeed 610.

Throughout this description, it is to be understood that any vaporstream generated in the process, such as in each distillation apparatus,can be condensed, and the condensation can occur inside the column,outside the column, such as after the vapor is discharged from therectification section of the distillation apparatus, and it can bepartially or fully condensed. Alternatively, the vapor stream does nothave to be condensed at all. It is also to be understood that any valuesdescribing the concentration of an ingredient in a vapor stream can bemeasured on a liquid stream condensed from the vapor stream in questionif the condensables in the vapor stream are fully condensed.

Alcohol recovery zone 800 generates a purified alcohol compositionstream 802 that is suitable for use as a recycle stream fed to theesterification zone 500 if desired, and a water rich stream 801 that isenriched in the concentration of water relative to the concentration ofwater in the purified alcohol composition stream 802. The concentrationof water in the water rich stream 801 is desirably at least 98 wt. %, orat least 99 wt. %, or at least 99.5 wt. %.

Examples of suitable devices to separate alcohol from water in thealcohol recovery zone include a distillation column, with trays, orpacked or both.

The vaporous purified alcohol composition stream 802, whether or notcondensed to use as a recycle stream to the esterification zone,contains less than 10 wt. % water, or less than 5 wt. % water, or lessthan 1 wt. % water, or less than 0.5 wt. % water, and less than 0.001wt. % DAFD, or less than 0.0001 wt. % DAFD, each based on the weight ofthe purified alcohol composition stream 802. In one embodiment, thepurified alcohol recycle stream 802 comprises methanol at a purity ofgreater than 99.0 wt. % based on the weight of the purified alcoholcomposition stream.

The second liquid DAFD rich composition stream 711 discharged from thealcohol water removal zone 710 contains DAFD at a concentration of atleast 80 wt. %, or at least 85 wt. %, or at least 90 wt. %, or at least92 wt. %, and up to 99 wt. %, or up to 98 wt. %, or up to 97 wt. %, orup to 96 wt. %, each based on the weight of the second liquid DAFD richcomposition stream 711. The amount of alcohol in the second liquid DAFDrich composition stream is desirably less than 1 wt. %, or less than 0.1wt. %, or less than 0.01 wt. %, or less than 0.001 wt. %. The amount ofwater in the second liquid DAFD rich composition 711 is desirably lessthan 1 wt. %, or less than 0.5 wt. %, or less than 0.2 wt. %. Theconcentration of DAFD in the second liquid DAFD rich composition 711 canbe higher than the concentration of DAFD in the first liquid DAFD richcomposition stream 620 by at least 10 wt %, or at least 20 wt %, or atleast 30 wt %, or at least 40 wt %. The cumulative concentration ofwater and alcohol in the second liquid DAFD rich composition 711 isdepleted relative to the concentration of water an alcohol in the firstliquid DAFD rich composition 620 by a factor of at least 100×, or atleast 300×, or at least 500×, or at least 700×.

The second liquid DAFD rich composition stream 711 contains not onlyDAFD, but also ACFC, AFC, and AFFC. As shown in FIG. 3 , the secondliquid DAFD rich composition 711 is fed to an AFC/AFFC removal zone 720to separate at least a portion of AFC from the liquid DAFD richcomposition using a physical separation process to produce an AFC richvapor composition 722 rich in the concentration of AFC relative to theconcentration of AFC in the second liquid DAFD rich composition 711, anda partially purified liquid DAFD rich composition stream 721 comprisingDAFD and ACFC that is rich in the concentration of DAFD relative to theconcentration of DAFD in the second liquid DAFD rich composition 711.Since AFC rich vapor composition 722 is rich in the concentration of AFCrelative to the concentration of AFC in the second liquid DAFD richcomposition 711, it is necessarily also rich in the concentration of AFCrelative to the concentration of AFC in the first liquid DAFD richcomposition stream 620. Since DAFD in the partially purified liquid DAFDrich composition stream 721 is rich in the concentration of DAFDrelative to the concentration of DAFD in the second liquid DAFD richcomposition 711, it is necessarily also rich in the concentration ofDAFD relative to the concentration of DAFD in the first liquid DAFD richcomposition stream 620.

An example of a suitable physical separation method is to distill thesecond liquid DAFD rich composition 711. Suitable distillation pottemperatures range in zone 720 from 200° C. to less than the boilingpoint of DAFD under the operating conditions. Suitable temperaturesrange from 210° C. to 280° C., or 220° C. to 260° C., or 230° C. to 250°C. The second liquid DAFD rich composition is desirably distilled at avacuum to avoid degrading the DAFD product in the second DAFD richcomposition in the pot that might otherwise occur at highertemperatures. The second DAFD rich composition can be distilled atpressures ranging from 1 psia to atmospheric pressure. The columndesirably has 10 to 70 trays, 10 to 60 trays to, 10 to 50 trays, where atray can be a valve tray, sieve tray, bubble cap tray, or an equivalentheight of a packed bed. The distillation operating temperature desirablyis set create an AFC vapor composition and desirably to take off AFCvapor as a distillate, which can optionally be partially or fullycondensed and a portion returned to the column as reflux. In anotherembodiment, the distillation conditions can be set to also take off AFFCin addition to AFC as a vapor overhead such that the concentration ofAFFC in the AFC rich vapor composition 722 is enriched in theconcentration of AFFC relative to the concentration of AFFC in thesecond liquid DAFD rich stream 711. In this embodiment, since AFC richvapor composition 722 is rich in the concentration of AFFC relative tothe concentration of AFFC in the second liquid DAFD rich composition711, it is necessarily also rich in the concentration of AFFC relativeto the concentration of AFFC in the first liquid DAFD rich compositionstream 620.

The reflux ratio to achieve desired purities will vary with the numberof trays and the mass of distillate produced.

The composition of the AFC rich vapor stream 722 contains AFC. The AFCrich vapor stream composition comprises at least 5 wt. % AFC, or atleast 10 wt. % AFC, or at least 15 wt. % AFC, or at least 20 wt. % AFC,or at least 25 wt. % AFC. The AFC rich vapor stream compositionoptionally comprises at least 2 wt. % AFFC, or at least 5 wt. % AFFC, orat least 10 wt. % AFFC, or at least 20 wt. % AFFC, or at least 30 wt. %AFFC, or at least 40 wt. % AFFC, or at least 50 wt. % AFFC, or at least60 wt. % AFFC. The concentration of AFFC in the AFC rich vapor stream722 can be higher than the concentration of AFC, in some cases by afactor of 1.5×, or 2×, or 2.5×. The concentration of DAFD in the AFCrich vapor composition 722 is depleted relative to the concentration ofDAFD in the second liquid DAFD rich composition stream 711. Theconcentration of DAFD in the AFC rich vapor composition 722 can be lessthan 10 wt. % DAFD, or less than 5 wt. % DAFD, or less than 4 wt. %DAFD, or less than 3 wt. % DAFD, or less than 2 wt. % DAFD, or less than1 wt. % DAFD, each based on the weight of the AFC rich vaporcomposition. The concentration of AFC and AFFC in the AFC rich vaporcomposition stream 722 can be at least 20 wt %, or at least 40 wt. %, orat least 60 wt. %, or at least 80 wt. %, or at least 90 wt. %, or atleast 95 wt. %, each based on the weight of all ingredients in the AFCrich vapor composition 722.

The concentration of AFC in the AFC rich vapor composition stream 722 isdesirably increased by a factor of at least 5×, or at least 10×, or atleast 15× and up to 80×, or up to 70×, or up to 50×, on a weight basis,relative to the concentration of AFC in the second liquid DAFD richcomposition 711.

The composition of the partially purified liquid DAFD rich stream 721contains DAFD and ACFC. The concentration of each of these ingredientsbased on the weight of the partially purified liquid DAFD rich stream721 is as follows:

-   -   DAFD: at least 90 wt. %, or at least 92 wt. %, or at least 95        wt. %, or at least 97 wt. %, or at least 98 wt. %, and up to        99.9 wt. %, or up to 99.5 wt. %, or up to 99.0 wt. %, or up to        98.5 wt. %, or up to 98 wt. %; and ACFC: at least 0.05 wt. %, or        at least 0.1 wt. %, or at least 0.5 wt. %, or at least 1.0 wt.        %, or at least 1.25 wt. %, and up to 10 wt. %, or up to 7 wt. %,        or up to 5.0 wt. %, or up to 4 wt. %, or up to 3 wt. %; and a        cumulative amount of AFFC, AFC, water and alcohol of less than 2        wt. %, or no more than 1.5 wt. %, or no more than 1.0 wt. %, or        no more than 0.5 wt. %, or no more than 0.1 wt %; and desirably        also AFC and AFFC in an amount of no more than 0.1 wt. %, or no        more than 0.05 wt. %, or no more than 0.001 wt. %.

The concentration of DAFD in the partially purified liquid DAFD richcomposition 721 is higher than the concentration of DAFD in the secondliquid DAFD rich composition 711. The concentration of AFC in thepartially purified liquid DAFD rich stream 721 is desirably depletedrelative to the concentration of AFC in the second liquid DAFD richcomposition 711 by a factor of at least 10×, or at least 100×, or atleast 250×, or at least 500×, or at least 750×, or at least 1000×.

The temperature of the partially purified liquid DAFD rich streameffluent 721 from the AFC/AFFC removal zone 720 is desirably at least220° C., or at least 230° C. and up to 270° C., or up to 260° C., or upto 250° C.

The partially purified liquid DAFD rich composition stream 721 is fed toan ACFC removal zone 730 to separate at least a portion of the DAFD fromthe partially purified liquid DAFD rich composition 721 using a physicalseparation process to produce a purified DAFD vapor composition 732 thatis rich in the concentration of DAFD relative to the concentration ofDAFD in the partially purified liquid DAFD rich composition 721, and aliquid ACFC bottoms stream 731 that is rich in the concentration of ACFCrelative to the concentration of ACFC in the partially purified liquidDAFD rich composition 721, each by weight. Since the purified DAFD vaporcomposition 732 is rich in the concentration of DAFD relative to theconcentration of DAFD in the partially purified liquid DAFD richcomposition stream 721, it is necessarily also rich in the concentrationof DAFD relative to the concentration of DAFD in the first liquid DAFDrich composition stream 620. Since the liquid ACFC bottoms stream 731 isrich in the concentration of ACFC relative to the concentration of ACFCin the partially purified liquid DAFD rich composition stream 721, it isnecessarily also rich in the concentration of ACFC relative to theconcentration of ACFC in the first liquid DAFD rich composition stream620.

An example of a suitable physical separation apparatus is a distillationcolumn. Suitable distillation pot temperatures range in zone 730 rangefrom 200° C. to less than the boiling point of ACFC under the operatingconditions. Desirably the temperature is set to at least the boilingpoint of the DAFD compound under the operating conditions. Suitable pottemperatures range from 210° C. to 280° C., or 220° C. to 260° C., or230° C. to 255° C. The partially purified liquid DAFD rich composition721 is desirably distilled at a vacuum to avoid degrading the DAFDproduct. The partially purified liquid DAFD rich composition 721 can bedistilled at pressures ranging from 1 psia to atmospheric pressure. Thecolumn desirably has 10 to 70 trays, 10 to 60 trays to, or 10 to 50trays, where a tray can be a valve tray, sieve tray, bubble cap tray, oran equivalent height of a packed bed. The distillation operatingtemperature desirably is set create a purified DAFD vapor compositionand desirably to take off DAFD vapor as a distillate, which canoptionally be partially or fully condensed and a portion returned to thecolumn as reflux. The reflux ratio will vary with the number of traysand the mass of distillate produced.

The composition of the purified DAFD vapor stream 732 contains DAFD. Theconcentration of each these ingredients by weight based on the weight ofthe purified DAFD vapor stream is as follows:

-   -   DAFD: at least 99.0 wt. %, or at least 99.2 wt. %, or at least        99.5 wt. %, or at least 99.7 wt. %, or at least 99.8 wt. %, or        at least 99.9 wt. %, and up to 99.999 wt. %, or up to 99.995 wt.        %, or at least 99.99 wt. %; and ACFC, that if present at all, is        present in an amount of greater than zero and not greater than        1000 ppm, or not greater than 100 ppm, or not greater than 10        ppm, or not greater than 1 ppm; and desirably AFFC, that if        present at all, is present in an amount of greater than zero and        not greater than 1000 ppm, or not greater than 100 ppm, or not        greater than 50 ppm, or not greater than 20 ppm.        -   Optionally, this composition also contains very low amounts            or no amount of: AFC, that if present at all, is present in            an amount of not greater than 10 ppm, or not greater than 1            ppm, or not greater than 0.1 ppm; and    -   alcohol, that if present at all, is present in an amount not        greater than 10 ppm, or not greater than 1 ppm, or not greater        than 0.1 ppm, and FDCA, if present at all, is present in an        amount of not greater than 1000 ppm, or not greater than 100        ppm, or not greater than 10 ppm, or not greater than 1 ppm.

Desirably, if water is present, it is present in an amount of notgreater than 1000 ppm, or not greater than 100 ppm, or not greater than10 ppm.

The concentration of ACFC in the purified DAFD vapor stream 732 isdepleted relative to the concentration of ACFC in the partially purifiedDAFD rich composition stream 721 by a factor of at least 10×, or atleast 50×, or at least 100×, or at least 200×.

The composition of the ACFC liquid bottoms composition 731 contains ACFCand DAFD. The ACFC liquid bottoms composition comprises ACFC in anamount of at least 20 wt. %, or at least 30 wt. %, or at least 40 wt. %based on the weight of the ACFC liquid bottoms composition. Theconcentration of DAFD in the ACFC liquid bottoms composition desirablycontains DAFD in an amount of less than 70 wt. %, or less than 50 wt. %,or less than 40 wt. %, or less than 30 wt. %, based on the weight of theACFC liquid bottoms composition. The amount of ACFC by weight isdesirably at least 1.5×, or at least 2.0× greater than the amount ofDAFD in the ACFC liquid bottoms stream.

The concentration of ACFC in ACFC liquid bottoms composition 731 isdesirably increased by a factor of at least 5×, or at least 10×, or atleast 30× relative to the concentration of ACFC in the partiallypurified liquid DAFD rich composition 721.

The purified DAFD vapor composition is desirably condensed in acondenser to produce a purified liquid DAFD product compositioncontaining liquefied DAFD at a temperature below the boiling point theDAFD compound and above its crystallization temperature at 1 atmosphere.The concentration of DAFD in the purified liquid DAFD productcomposition, based on the purified liquid DAFD product composition, is

-   -   DAFD: at least 99.0 wt. %, or at least 99.2 wt. %, or at least        99.5 wt. %, or at least 99.7 wt. %, or at least 99.8 wt. %, or        at least 99.9 wt. %, and up to 99.999 wt. %, or up to 99.995 wt.        %, or at least 99.99 wt. %; and ACFC, that if present at all, is        in an amount of not greater than 100 ppm, or not greater than 10        ppm, or not greater than 1 ppm; and desirably    -   AFFC, that if present, is present in an amount of not more than        1000 ppm, or not more than 100 ppm, or not more than 50 ppm, or        not more than 20 ppm, and    -   optionally, AFC, that if present at all, is present in an amount        of not greater than 10 ppm, or not greater than 1 ppm, or not        greater than 0.1 ppm; and    -   optionally, alcohol, that if present at all, is present in an        amount not greater than 10 ppm, or not greater than 1 ppm, or        not greater than 0.1 ppm; and desirably    -   FDCA, if present at all, is present in an amount of not greater        than 1000 ppm, or not greater than 100 ppm, or not greater than        10 ppm, or not greater than 1 ppm.

Desirably, if water is present in the purified liquid DAFD productcomposition, it is present in an amount of not greater than 1000 ppm, ornot greater than 100 ppm, or not greater than 10 ppm, or not greaterthan 5 ppm, or not greater than 1 ppm. The solids concentration in thepurified liquid DAFD product composition is desirably 0, but if solidsare present, they are present in an amount of less than 0.1 wt %, or notmore than 0.01 wt. %, or not more than 0.001 wt. %.

If desired, the purified liquid DAFD product composition can be hot. Thehot purified liquid DAFD product composition can be routed to a moltenproduct storage tank, to train tanker car or tanker truck capable ofcontaining and transferring hot liquid material, and/or directly to apolyester process through a pipeline wherein DAFD is mixed with apolyester raw material comprising a diol such as ethylene glycol andreacted with said diol to form polymer comprising polyester.

Alternatively, the purified DAFD vapor composition can be condensed andcrystallized to form DAFD solid particles comprising 99.9 wt. % DAFD ona solids basis as a slurry, or instead of a slurry, can be dried to forma dry DAFD solids stream, that in each case has a purity of at least thesame purity levels as in the purified DAFD vapor rich stream 732. Theconversion of the purified liquid DAFD composition into a dry solidstream can be accomplished by any other methods known in the artincluding a chilled belt flaker, spray drying, and the like. Thus, thereis also provided a solids DAFD composition comprising solid particles ofDAFD, wherein said solids comprise:

-   -   (i) at least 99.9 wt. % DAFD, or at least 99.95 wt. % DAFD, or        at least 99.99 wt. % DAFD;    -   (ii) not more than 1000 ppm, or not more than 100 ppm, or not        more than 10 ppm ACFC 5-(alkoxycarbonyl)furan-2-carboxylic acid,    -   (iii) alkyl-5-formylfuran-2-carboxylate (AFFC) that if present,        is present in an amount of not more than 1000 ppm, or not more        than 100 ppm, or not more than 10 ppm, and optionally    -   (iv) not more than 100 ppm, or not more than 100 ppm, or not        more than 10 ppm, alkyl furan-2-carboxylate, and        wherein the composition contains not more than 1 wt. % water, or        not more than 0.5 wt. % water, or not more than 0.1 wt % water,        or not more than 0.01 wt. % water. Desirably, the composition        contains less than 1000 ppm furan dicarboxylic acid (FDCA), or        less than 500 ppm FDCA, or less than 250 ppm FDCA, or less than        100 ppm FDCA, or less than 50 ppm FDCA, or less than 20 ppm        FDCA, or less than 10 ppm FDCA, or less than 5 ppm FDCA, or less        than 3 ppm FDCA.

The process of the invention is described in further detail in thisexample obtained by modeling using an ASPEN program:

For a given plant embodiment, a crude diester stream 510 is providedwhich comprises 199,628 kg methanol/day; 11,346 kg water/day; 508 kgMFC/day; 1,490 kg MFFC/day; 50,614 kg DMFD/day; 954 kg MCFC/day; and 479kg FDCA impurities/day. The crude diester stream 510 is at a temperatureof 230° C. and under a pressure of 2,000 psia. The crude diester streamis fed to a flash evaporation zone 600 where the pressure of the streamis reduced to 40 psia and by flash evaporation is split into twostreams: an vapor alcohol stream 610 that comprises 164,502 kgmethanol/day; 7,959 kg water/day; 87 kg MFC/day; 5 kg MFFC/day; and 134kg DMFD/day; and a first liquid DAFD rich composition stream 620 whichcomprises 35,126 kg methanol/day; 3,387 kg water/day; 421 kg MFC/day;1,485 kg MFFC/day; 50,480 kg DMFD/day; 954 kg MCFC/day; and 479 kg FDCAimpurities/day.

The first liquid DAFD rich composition stream 620 is fed to adistillation column in the alcohol water removal zone 710 having 38trays and set to a top pressure of 12 psia. The liquid bottomstemperature is 225° C. Methanol and water are removed as a secondalcohol rich distillate stream 712 comprising 35,126 kg methanol/day;3,338 kg water/day; and 18 kg MFC/day. The distillation column underflowliquid stream, the second liquid DAFD rich composition 711, comprises 49kg water/day; 403 kg MFC/day; 1,485 kg MFFC/day; 50,480 kg DMFD/day; 954kg MCFC/day; and 479 kg FDCA impurities/day.

The vapor alcohol stream 610 and second alcohol rich stream 712 are fedto a distillation column in the alcohol recovery zone 800 for alcoholrecovery and water purge. The distillation column has 48 trays, is setat a top pressure of 8 psia, and has a liquid bottoms temperature of 95°C. The alcohol recycle distillate stream 802 comprises 199,627 kgmethanol/day; and 1,122 kg water/day. The underflow water rich purgestream 801 comprises 10,174 kg water/day; 105 kg MFC/day; 5 kg MFFC/day;and 134 kg DMFD/day.

The second liquid DAFD rich stream 711 is fed to a distillation columnin the AFC/AFFC removal zone 720. The distillation column has 48 trays,is set at a top pressure of 3 psia, and has a liquid bottoms temperatureof 242° C. The column distillate stream, the AFC rich vapor composition722, comprises 49 kg water/day; 403 kg MFC/day; 1,484 kg MFFC/day; 73 kgDMFD/day; and 9 kg FDCA impurities/day as a process purge of impurities.The column underflow stream, the partially purified liquid DAFD richcomposition 721, comprises 1 kg MFFC/day; 50,480 kg DMFD/day; 954 kgMCFC/day; and 470 kg FDCA impurities/day.

The partially purified liquid DAFD rich composition stream 721 is fed toa distillation column in ACFC removal zone 730. The distillation columnhas 23 trays, is set at a top pressure of 1 psia, and has a liquidbottoms temperature of 248° C. The column distillate stream, the DAFDrich vapor 732, is the plant DMFD product stream and comprises 1 kgMFFC/day; 50,000 kg DMFD/day; 3 kg MCFC/day; and 5 kg FDCAimpurities/day. The column underflow stream, ACFC liquid bottoms stream731, comprises 408 kg DMFD/day; 951 kg MCFC/day; and 465 kg FDCAimpurities/day.

The invention also includes a process for the manufacture of FDCA, whichis one of the raw materials fed to the esterification zone 500. Theprocess for the manufacture of FDCA will now be described in moredetail.

The process comprises feeding an oxidizable composition to an oxidationzone, where the oxidizable composition contains a compound having afuran moiety. The furan moiety can be represented by the structure:

The compounds having a furan moiety are such that, upon oxidation, formcarboxylic acid functional groups on the compound. Examples of compoundshaving furnan moieties include 5-(hydroxymethyl)furfural (5-HMF), andderivatives of 5-HMF. Such derivatives include esters of 5-HMF, such asthose represented by the formula 5-R(CO)OCH₂-furfural where R=alkyl,cycloalkyl and aryl groups having from 1 to 8 carbon atoms, or 1-4carbon atoms or 1-2 carbon atoms; ethers of 5-HMF represented by theformula 5-R′OCH₂-furfural, where R′=alkyl, cycloalkyl and aryl havingfrom 1 to 8 carbon atoms, or 1-4 carbon atoms or 1-2 carbon atoms);5-alkyl furfurals represented by the formula 5-R″-furfural, whereR″=alkyl, cycloalkyl and aryl having from 1 to 8 carbon atoms, or 1-4carbon atoms or 1-2 carbon atoms). Thus the oxidizable composition cancontain mixtures of 5-HMF and 5-HMF esters; 5-HMF and 5-HMF ethers;5-HMF and 5-alkyl furfurals, or mixtures of 5-HMF and its esters,ethers, and alkyl derivatives.

The oxidizable composition, in addition to 5-(hydroxymethyl)furfural(5-HMF) or an of its derivatives, may also contain5-(acetoxymethyl)furfural (5-AMF) and 5-(ethoxymethyl)furfural (5-EMF).

Specific examples of 5-HMF derivatives include those having thefollowing structures:

One embodiment is illustrated in FIG. 1 . An oxidizable composition isfed to a primary oxidation zone 100 and reacted in the presence of asolvent, a catalyst system, and a gas comprising oxygen, to generate acrude dicarboxylic acid stream 110 comprising furan-2,5-dicarboxylicacid (FDCA).

For example, the oxidizable composition containing 5-HMF, or itsderivatives, or combinations thereof, are oxidized with elemental O₂ ina multi-step reaction to form FDCA with 5-formyl furan-2-carboxylic acid(FFCA) as a key intermediate, represented by the following sequence:

If desired, the oxygen gas stream 10 comprising oxygen, a solvent stream30, and the oxidizable stream 20 can be fed to the primary oxidationzone 100 as separate streams. Or, an oxygen stream 10 comprising oxygenas one stream and an oxidizable stream 20 comprising solvent, catalyst,and oxidizable compounds as a second stream can be fed to the primaryoxidation zone 100. Accordingly, the solvent, oxygen gas comprisingoxygen, catalyst system, and oxidizable compounds can be fed to theprimary oxidization zone 100 as separate and individual streams orcombined in any combination prior to entering the primary oxidizationzone 100 wherein these feed streams may enter at a single location or inmultiple locations into the primary oxidizer zone 100.

The catalyst can be a homogenous catalyst soluble in the solvent or aheterogeneous catalyst. The catalyst composition is desirably soluble inthe solvent under reaction conditions, or it is soluble in the reactantsfed to the oxidation zone. Preferably, the catalyst composition issoluble in the solvent at 40° C. and 1 atm, and is soluble in thesolvent under the reaction conditions.

Suitable catalysts components comprise at least one selected from, butare not limited to, cobalt, bromine and manganese compounds. Preferablya homogeneous catalyst system is selected. The preferred catalyst systemcomprises cobalt, manganese and bromine.

The cobalt atoms may be provided in ionic form as inorganic cobaltsalts, such as cobalt bromide, cobalt nitrate, or cobalt chloride, ororganic cobalt compounds such as cobalt salts of aliphatic or aromaticacids having 2-22 carbon atoms, including cobalt acetate, cobaltoctanoate, cobalt benzoate, cobalt acetylacetonate, and cobaltnaphthalate. The oxidation state of cobalt when added as a compound tothe reaction mixture is not limited, and includes both the +2 and +3oxidation states.

The manganese atoms may be provided as one or more inorganic manganesesalts, such as manganese borates, manganese halides, manganese nitrates,or organometallic manganese compounds such as the manganese salts oflower aliphatic carboxylic acids, including manganese acetate, andmanganese salts of beta-diketonates, including manganeseacetylacetonate.

The bromine component may be added as elemental bromine, in combinedform, or as an anion. Suitable sources of bromine include hydrobromicacid, sodium bromide, ammonium bromide, potassium bromide, andtetrabromoethane. Hydrobromic acid, or sodium bromide may be preferredbromine sources.

The amount of bromine atoms desirably ranges from at least 300 ppm, orat least 2000 ppm, or at least 2500 ppm, or at least 3000 ppm, or atleast 3500 ppm, or at least 3750, ppm and up to 4500 ppm, or up to 4000ppm, based on the weight of the liquid in the reaction medium of theprimary oxidation zone. Bromine present in the an amount of 2500 ppm to4000 ppm, or 3000 ppm to 4000 ppm are especially desirable to promotehigh yield.

The amount of cobalt atoms can range from at least 500 ppm, or at least1500 ppm, or at least 2000 ppm, or at least 2500 ppm, or at least 3000ppm, and up to 6000 ppm, or up to 5500 ppm, or up to 5000 ppm, based onthe weight of the liquid in the reaction medium of the primary oxidationzone. Cobalt present in an amount of 2000 to 6000 ppm, or 2000 to 5000ppm are especially desirable to promote high yield.

The amount of manganese atoms can range from 2 ppm, or at least 10 ppm,or at least 30 ppm, or at least 50 ppm, or at least 70 ppm, or at least100 ppm, and in each case up to 600 ppm, or up to 500 ppm or up to 400ppm, or up to 350 ppm, or up to 300 ppm, or up to 250 ppm, based on theweight of the liquid in the reaction medium of the primary oxidationzone. Manganese present in an amount ranging from 30 ppm to 400 ppm, or70 ppm to 350 ppm, or 100 ppm to 350 ppm is especially desirable topromote high yield.

The weight ratio of cobalt atoms to manganese atoms in the reactionmixture can be from 1:1 to 400:1, or 10:1 to about 400:1. A catalystsystem with improved Co:Mn ratio can lead to high yield of FDCA. Toincrease the yield of FDCA, when the oxidizable composition fed to theoxidation reactor comprises 5-HMF, then the cobalt to manganese weightratio is at least 10:1, or at least 15:1, or at least 20:1, or at least25:1, or at least 30:1, or at least 40:1 or at least 50:1, or at least60:1, and in each case up to 400:1. However, in the case where theoxidizable composition comprises esters of 5-HMF, ethers of 5-HMF, or5-alkyl furfurals, or mixtures of any of these compounds together orwith 5-HMF, the cobalt to manganese weight ratio can be lowered whilestill obtaining high yield of FDCA, such as a weight ratio of Co:Mn ofat least 1:1, or at least 2:1, or at least 5:1, or at least 9:1, or atleast 10:1, or at least 15:1, or at least 20:1, or at least 25:1, or atleast 30:1, or at least 40:1, or at least 50:1, or at least 60:1 and ineach case up to 400:1.

The weight ratio of cobalt atoms to bromine atoms is desirably at least0.7:1, or at least 0.8:1, or at least 0.9:1, or at least 1:1,or at least1.05:1, or at least 1.2:1,or at least 1.5:1,or at least 1.8:1,or atleast 2:1,or at least 2.2:1,or at least 2.4:1,or at least 2.6:1,or atleast 2.8:1,and in each case up to 3.5, or up to 3.0, or up to 2.8.

The weight ratio of bromine atoms to manganese atoms is from about 2:1to 500:1.

Desirably, the weight ratio of cobalt to manganese is from 10:1 to400:1, and the weight ratio of cobalt to bromine atoms ranges from 0.7:1to 3.5:1. Such a catalyst system with improved Co:Mn and Co:Br ratio canlead to high yield of FDCA (minimum of 90%), decrease in the formationof impurities (measured by b*) causing color in the downstreampolymerization process while keeping the amount of CO and CO₂ (carbonburn) in the off-gas at a minimum.

Desirably, the amount of bromine present is at least 1000 ppm and up to3500 ppm, and the weight ratio of bromine to manganese is from 2:1 to500:1. This combination has the advantage of high yield and low carbonburn.

Desirably, the amount of bromine present is at least 1000 ppm and up to3000 ppm, and the amount of cobalt present is at least 1000 ppm and upto 3000 ppm, and the weight ratio of cobalt to manganese is from 10:1 to100:1. This combination has the advantage of high yield and low carbonburn.

Suitable solvents include aliphatic solvents. In an embodiment of theinvention, the solvents are aliphatic carboxylic acids which include,but are not limited to, C₂ to C₆ monocarboxylic acids, e.g., aceticacid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid,trimethylacetic acid, caprioic acid, and mixtures thereof.

The most common solvent used for the oxidation is an aqueous acetic acidsolution, typically having a concentration of 80 to 99 wt. %. Inespecially preferred embodiments, the solvent comprises a mixture ofwater and acetic acid which has a water content of 0% to about 15% byweight. Additionally, a portion of the solvent feed to the primaryoxidation reactor may be obtained from a recycle stream obtained bydisplacing about 80 to 90% of the mother liquor taken from the crudereaction mixture stream discharged from the primary oxidation reactorwith fresh, wet acetic acid containing about 0% to 15% water.

The oxidizing gas stream comprises oxygen. Examples include, but are notlimited to, air and purified oxygen. The amount of oxygen in the primaryoxidation zone ranges from about 5 mole % to 45 mole %, 5 mole % to 60mole %, or 5 mole % to 80 mole %.

The temperature of the reaction mixture in the primary oxidation zonecan vary from about 100° C. to about 220° C. The temperature of thereaction mixture in the primary oxidation zone is at least 100° C., orat least 105° C., or at least 110° C., or at least 115° C., or at least120° C., or at least 125° C., or at least 130° C., or at least 135° C.,or at least 140° C., or at least 145° C., or at least 150° C., or atleast 155° C., or at least 160° C., and can be as high as 220° C., or upto 210° C., or up to 200° C., or up to 195° C., or up to 190° C., or upto 180° C., or up to 175° C., or up to 170° C., or up to 165° C., or upto 160° C., or up to 155° C., or up to 150° C., or up to 145° C., or upto 140° C., or up to 135° C., or up to 130° C. In other embodiments, thetemperate ranges from 105° C. to 180° C., or from 105° C. to 175° C., orfrom 105° C. to 160° C., or from 105° C. to 165° C., or from 105° C. to160° C., or from 105° C. to 155° C., or from 105° C. to 150° C., or from110° C. to 180° C., or from 110° C. to 175° C., or from 110° C. to 170°C., or from 110° C. to 165° C., or from 110° C. to 160° C., or from 110°C. to 155° C., or from 110° C. to 150° C., or from 110° C. to 145° C.,or from 115° C. to 180° C., or from 115° C. to 175° C., or from 115° C.to 170° C., or from 115° C. to 167° C., or from 115° C. to 160° C., orfrom 115° C. to 155° C., or from 110° C. to 150° C., or from 115° C. to145° C., or from 120° C. to 180° C., or from 120° C. to 175° C., or from120° C. to 170° C., or from 120° C. to 165° C., or from 120° C. to 160°C., or from 120° C. to 155° C., or from 120° C. to 150° C., or from 120°C. to 145° C., or from 125° C. to 180° C., or from 125° C. to 175° C.,or from 125° C. to 170° C., or from 125° C. to 165° C., or from 125° C.to 160° C., or from 125° C. to 155° C., or from 125° C. to 150° C., orfrom 125° C. to 145° C., or from 130° C. to 180° C., or from 130° C. to175° C., or from 130° C. to 170° C., or from 130° C. to 165° C., or from130° C. to 160° C., or from 130° C. to 155° C., or from 130° C. to 150°C., or from 130° C. to 145° C., or from 135° C. to 180° C., or from 135°C. to 175° C., or from 135° C. to 170° C., or from 135° C. to 170° C.,or from 135° C. to 165° C., or from 135° C. to 160° C., or from 135° C.to 155° C., or from 135° C. to 150° C., or from 135° C. to 145° C., orfrom 140° C. to 180° C., or from 140° C. to 175° C., or from 140° C. to170° C., or from 140° C. to 170° C., or from 140° C. to 165° C., or from140° C. to 160° C., or from 140° C. to 155° C., or from 140° C. to 150°C., or from 140° C. to 145° C., or from 145° C. to 180° C., or from 145°C. to 175° C., or from 145° C. to 170° C., or from 145° C. to 170° C.,or from 145° C. to 165° C., or from 145° C. to 160° C., or from 145° C.to 155° C., or from 145° C. to 150° C., or from 150° C. to 180° C., orfrom 150° C. to 175° C., or from 150° C. to 170° C., or from 150° C. to165° C., or from 150° C. to 160° C., or from 150° C. to 155° C., or from155° C. to 180° C., or from 155° C. to 175° C., or from 155° C. to 170°C., or from 155° C. to 165° C., or from 155° C. to 160° C., or from 160°C. to 180° C., or from 160° C. to 175° C., or from 160° C. to 170° C.,or from 160° C. to 165° C., or from 165° C. to 180° C., or from 165° C.to 175° C., or from 165° C. to 170° C., or from 165° C. to 180° C., orfrom 165° C. to 175° C., or from 165° C. to 170° C., or from 170° C. to180° C., or from 170° C. to 175° C., or from 175° C. to 180° C.

To minimize carbon burn, it is desired that the temperature of thereaction mixture is not greater than 165° C., or not greater than 160°C. In the process of the invention, the contents of the oxidizer off gascomprise COx, wherein x is 1 or 2, and the amount of COx in the oxidizeroff gas is less than 0.05 moles of COx per mole of the total oxidizablefeed to the reaction medium, or no more than 4 moles of COx per mole ofthe total oxidizable feed to the reaction medium, or no more than 6moles of COx per mole of the total oxidizable feed to the reactionmedium. The carbon burn as determined by the COx generation rate can becalculated as follows: (moles of CO+ moles of CO2)/moles of oxidizablefeed. The low carbon burn generation rate in the process of theinvention is achievable by the combination of low reaction temperature,and the molar weight ratios of the catalyst components as describedabove.

The oxidation reaction can be conducted under a pressure ranging from 40to 300 psia. A bubble column is desirably operated under a pressureranging from 40 psia to 150 psia. In a stirred tank vessel, the pressureis desirably set to 100 psia to 300 psia.

Oxidizer off gas stream 120 containing COx (CO and CO₂), water,nitrogen, and vaporized solvent, is routed to the oxidizer off gastreatment zone 1000 to generate an inert gas stream 810, liquid stream820 comprising water, and a recovered oxidation solvent stream 830comprising condensed solvent. In one embodiment, oxidizer off gas stream120 can be fed to directly, or indirectly after separating condensablessuch as solvent from non-condensables such as COx and nitrogen in aseparation column (e.g. distillation column with 10-200 trays), to anenergy recovery device such as a turbo-expander to drive an electricgenerator. Alternatively or in addition, the oxidizer off gas stream canbe fed to a steam generator before or after the separation column togenerate steam, and if desired, may then be fed to a turbo-expander andpre-heated prior to entry in the expander if necessary to ensure thatthe off gas does not condense in the turbo-expander.

In another embodiment, at least a portion of the oxidation solventstream 830 recovered from the oxidizer off-gas stream is routed to afilter and then to a wash solvent stream 320 to become a portion of thewash solvent stream 320 for the purpose of washing the solids present inthe solid-liquid separation zone. In another embodiment, the inert gasstream 810 can be vented to the atmosphere. In yet another embodiment,at least a portion of the inert gas stream 810 can be used as an inertgas in the process for inerting vessels and or used for convey gas forsolids in the process.

The oxidation can be conducted in a continuous stirred tank reactor orin a bubble column reactor.

The FDCA formed by the oxidation reaction desirably precipitates out ofthe reaction mixture. The reaction mixture comprises the oxidizablecomposition, solvent, and catalyst if a homogeneous catalyst is used,otherwise it comprises the oxidizable composition and solvent.

The product of the oxidation reaction is a crude dicarboxylic acidstream 110 comprising FDCA as a solid, FDCA dissolved in the solvent,solvent, and by-products and intermediate products, and homogeneouscatalyst system if used. Examples of by-products include levulinic acid,succinic acid, and acetoxy acetic acid. Examples of intermediateproducts include 5-formyl furan-2-carboxylic acid (FFCA) and2,5-diformylfuran.

The percent solids in the crude dicarboxylic acid stream ranges is atleast 10 wt %, or at least 15 wt. %, or at least 20 wt. %, or at least25 wt. %, or at least 28 wt. %, or at least 30 wt. %, or at least 32 wt.%, or at least 35 wt. %, or at least 37 wt. %, or at least 40 wt. %.While there is no upper limit, as a practice the amount will not exceed60 wt. %, or no greater than 55 wt. %, or no greater than 50 wt. %, orno greater than 45 wt. %, or not greater than 43 wt. %, or not greaterthan 40 wt %, or not greater than 39 wt %. Of the solids in the crudedicarboxylic acid stream, it is desirable that at least 80 wt. %, or atleast 85 wt. %, or at least 90 wt. %, or at least 95 wt. % of the solidsin each case is FDCA.

The stated amount of each of the following intermediates, product, andimpurities are based on the weight of the solids in the crude carboxylicacid composition produced in the primary oxidation reactor in theoxidation zone 100.

The amount of the intermediate FFCA present in the crude dicarboxylicacid stream is not particularly limited. Desirably, the amount is lessthan 4 wt. %, or less than 3.5 wt. %, or less than 3.0 wt. %, or lessthan 2.5 wt. %, or up to 2.0 wt. %, or up to 1.5 wt. %, or up to 1.0 wt.%, or up to 0.8 wt. %, based on the weight of the solids present in thecrude dicarboxylic acid stream.

Impurities, if present in the crude dicarboxylic acid composition,include such compounds as 2,5-diformylfuran, levulinic acid, succinicacid, and acetoxy acetic acid. These compounds can be present, if atall, in an amount of 0 wt % to about 0.2 wt % 2,5 difrmylfuran,levulinic acid in an amount ranging from 0 wt % to 0.5 wt %, succinicacid in an amount ranging from 0 wt % to 0.5 wt % and acetoxy aceticacid in an amount ranging from 0 wt % to 0.5 wt %, and a cumulativeamount of these impurities in an amount ranging from 0 wt. % to 1 wt. %,or from 0.01 wt % to 0.8 wt. %, or from 0.05 wt % to 0.6 wt. %, eachbased on the weight of the solids present in the crude dicarboxylic acidstream.

In another embodiment of the invention the crude dicarboxylic acidcomposition 110 comprises FDCA, FFCA and5-(ethoxycarbonyl)furan-2-carboxylic acid (“EFCA”). The EFCA in thecrude dicarboxylic acid composition 110 can be present in an amount ofat least 0.05 wt %, or at least 0.1 wt %, or at least 0.5 wt % and ineach case up to about 4 wt %, or up to about 3.5 wt %, or up to 3 wt. %,or up to 2.5 wt %, or up to 2 wt. %, based on the weight of the solidspresent in the crude dicarboxylic acid stream.

The yield of FDCA, on a solids basis and measured after the drying zonestep, is at least 60%, or at least 65%, or at least 70%, or at least72%, or at least 74%, or at least 76%, or at least 78%, or at least 80%,or at least 81%, or at least 82%, or at least 83%, or at least 84%, orat least 85%, or at least 86%, or at least 87%, or at least 88%, or atleast 89%, or at least 90%, or at least 91%, or at least 92%, or atleast 94%, or at least 95%, and up to 99%, or up to 98%, or up to 97%,or up to 96%, or up to 95%, or up to 94%, or up to 93%, or up to 92%, orup to 91%, or up to 90%, or up to 89%. For example, the yield can rangefrom 70% up to 99%, or 74% up to 98%, or 78% up to 98%, or 80% up to98%, or 84% up to 98%, or 86% up to 98%,or 88% up to 98%, or 90% up to98%, or 91% up to 98%, or 92% up to 98%, or 94% up to 98%, or 95% up to99%.

Yield is defined as mass of FDCA obtained divided by the theoreticalamount of FDCA that should be produced based on the amount of rawmaterial use. For example, if one mole or 126.11 grams of 5-HMF areoxidized, it would theoretically generate one mole or 156.01 grams ofFDCA. If for example, the actual amount of FDCA formed is only 150grams, the yield for this reaction is calculated to be=(150/156.01)times 100, which equals a yield of 96%. The same calculation applies foroxidation reaction conducted using 5-HMF derivatives or mixed feeds.

The maximum b* of the dried solids, or wet cake, is not particularlylimited. However, a b* of not more than 20, or no more than 19, or nomore than 18, or no more than 17, or no more than 16, or no more than15, or no more than 10, or no more than 8, or no more than 6, or no morethan 5, or no more than 4, or no more than 3, is desirable withouthaving to subject the crude carboxylic acid composition tohydrogenation. However, if lowered b* is important for a particularapplication, the crude carboxylic acid composition can be subjected tohydrogenation.

The b* is one of the three-color attributes measured on a spectroscopicreflectance-based instrument. The color can be measured by any deviceknown in the art. A Hunter Ultrascan XE instrument is typically themeasuring device. Positive readings signify the degree of yellow (orabsorbance of blue), while negative readings signify the degree of blue(or absorbance of yellow).

In the next step, which is an optional step, the crude dicarboxylic acidstream 110 can fed to a cooling zone 200 to generate a cooled crudedicarboxylic acid slurry stream 210 and a 1^(st) solvent vapor stream220 comprising solvent vapor. The cooling of crude carboxylic slurrystream 110 can be accomplished by any means known in the art. Typically,the cooling zone 200 is a flash tank. All or a portion of the crudedicarboxylic acid stream 110 can be fed to the cooling zone.

All or a portion of the crude dicarboxylic acid stream 110 can be fed tosolid-liquid separation zone 300 without first being fed to a coolingzone 200. Thus, none or only a portion can be cooled in cooling zone200. The temperature of stream 210 exiting the cooling zone can rangefrom 35° C. to 160° C., 55° C. to 120° C., and preferably from 75° C. to95° C.

The crude dicarboxylic acid stream 110, or 210 if routed through acooling zone, is fed to a solid-liquid separation zone 300 to generate acrude carboxylic acid wet cake stream 310 comprising FDCA. The functionsof isolating, washing and dewatering the crude carboxlic acid stream maybe accomplished in a single solid-liquid separation device or multiplesolid-liquid separation devices. The solid-liquid separation zone 300comprises at least one solid-liquid separation device capable ofseparating solids and liquids, washing solids with a wash solvent stream320, and reducing the % moisture in the washed solids to less than 30weight %. Desirably, the solid-liquid separation device is capable ofreducing the % moisture down to less than 20 weight %, or less than 15weight %, and preferably 10 weight % or less. Equipment suitable for thesolid liquid separation zone can typically be comprised of, but notlimited to, the following types of devices: centrifuges of all typesincluding but not limited to decanter and disc stack centrifuges, solidbowl centrifuges, cyclone, rotary drum filter, belt filter, pressureleaf filter, candle filter, and the like. The preferred solid liquidseparation device for the solid liquid separation zone is a continuouspressure drum filter, or more specifically a continuous rotary pressuredrum filter. The solid-liquid separator may be operated in continuous orbatch mode, although it will be appreciated that for commercialprocesses, the continuous mode is preferred.

The temperature of crude carboxylic acid slurry stream, if cooled asstream 210, fed to the solid-liquid separation zone 300 can range from35° C. to 160° C., 55° C. to 120° C., and is preferably from 75° C. to95° C.

The wash stream 320 comprises a liquid suitable for displacing andwashing mother liquor from the solids. For example, the wash solventcomprises acetic acid, or acetic acid and water, an alcohol, or water,in each case up to an amount of 100%. The temperature of the washsolvent can range from 20° C. to 180° C., or 40° C. and 150° C., or 50°C. to 130° C. The amount of wash solvent used is defined as the washratio and equals the mass of wash divided by the mass of solids on abatch or continuous basis. The wash ratio can range from about 0.3 toabout 5, about 0.4 to about 4, and preferably from about 0.5 to 3.

There can be multiple washes with the same wash solvent or withdifferent wash solvents. For example a first wash comprising acetic acidmay be followed by a second wash comprising the alcohol utilized in thedownstream esterification reaction zone.

After solids are washed in the solid liquid separation zone 300, theyare dewatered. Dewatering can take place in the solid liquid separationzone or it can be a separate device from the solid-liquid separationdevice. Dewatering involves reducing the mass of moisture present withthe solids to less than 30% by weight, less than 25% by weight, lessthan 20% by weight, and most preferably less than 15% by weight so as togenerate a crude carboxylic acid wet cake stream 310 comprising FDCA.Dewatering can be accomplished in a filter by passing a gas streamthrough the solids to displace free liquid after the solids have beenwashed with a wash solvent. Alternatively, dewatering can be achieved bycentrifugal forces in a perforated bowl or solid bowl centrifuge.

One or more washes may be implemented in solid-liquid separation zone300. One or more of the washes, preferably at least the final wash, insolid-liquid separation zone 300 comprises a hydroxyl functionalcompound as defined further below, such as an alcohol (e.g. methanol).By this method, a wet cake stream 310 is produced comprising thehydroxyl functional compound such as methanol in liquid form. The amountof the hydroxyl functional compound in liquid form in the wet cake canbe at least 50 wt %, or at least 75 weight %, or at least 85% weight %,or at least 95 weight % hydroxyl functional compound such as methanolbased on the weight of the liquids in the wet cake stream. The advantageof adopting this technique of washing with a hydroxyl functionalcompound is that a portion or all of the wet cake can be fed to theesterification zone 500 without undergoing, or by-pass, a step offeeding the wet cake to a vessel for drying the wet cake in a dryingzone 400 after the solid-liquid separation zone.

In one embodiment, 100% of wet cake stream 310 is fed to esterificationreaction zone 500 without undergoing or subjecting the wet cake to avessel for drying the wet cake from the solid liquid separation zone300.

Stream 330 generated in solid-liquid separation zone 300 is a liquidmother liquor stream comprising oxidation solvent, catalyst, andimpurities. If desired, a portion of mother liquor stream 330 can be fedto a purge zone 900 and a portion can be fed back to the primaryoxidation zone 100, wherein a portion is at least 5 weight % based onthe weight of the liquid. Wash liquor stream 340 is also generated inthe solid-liquid separation zone 300 and comprises a portion of themother liquor present in stream 210 and wash solvent wherein the weightratio of mother liquor mass to wash solvent mass in the wash liquorstream is less than 3 and preferably less than 2. From 5% to 95%, from30% to 90%, and most preferably from 40 to 80% of mother liquor presentin the crude carboxylic acid stream fed to the solid-liquid separationzone 200 is isolated in solid-liquid separation zone 300 to generatemother liquor stream 330 resulting in dissolved matter comprisingimpurities present in the displaced mother liquor not going forward inthe process. The mother liquor stream 330 contains dissolved impuritiesremoved from the crude dicarboxylic acid.

Sufficient hydroxyl functional compound such as an alcohol (e.g.methanol) is fed to the solid liquid separation zone 300 that becomesmixed with solids present resulting in a low impurity slurry stream 310being pumpable with weight % solids ranging from 1% to 50%, 10% to 40%,and preferably the weight % solids in stream 310 will range from 25% to38%.

In one embodiment, from 5% to 100% by weight of the displaced motherliquor stream 330 is routed to a purge zone 900 wherein a portion of theimpurities present in stream 330 are isolated and exit the process aspurge stream 920, wherein a portion is 5% by weight or greater.Recovered solvent stream 910 comprises solvent and catalyst isolatedfrom stream 330 and is recycled to the process. The recovered solventstream 910 can be recycled to the primary oxidation zone 100 andcontains greater than 30% of the catalyst that entered the purge zone900 in stream 330. The stream 910 recycled to the primary oxidation zone100 may contain greater than 50 weight %, or greater than 70 weight %,or greater than 90 weight % of the catalyst that enters the purge zone900 in stream 330 on a continuous or batch basis.

Optionally, a portion up to 100% of the crude carboxylic acidcomposition may be routed directly to a secondary oxidation zone (notshown) before being subjected to a solid liquid separation zone 300.

Generally, oxidation in a secondary oxidation zone is at a highertemperature than the oxidation in the primary oxidation zone 100 toenhance the impurity removal. In one embodiment, the secondary oxidationzone is operated at about 30° C., 20° C., and preferably 10° C. highertemperature than the oxidation temperature in the primary oxidation zone100 to enhance the impurity removal. The secondary oxidation zone can beheated directly with solvent vapor, or steam via stream or indirectly byany means known in the art.

Additional purification of the crude carboxylic acid stream can beaccomplished in the secondary oxidation zone by a mechanism involvingrecrystallization or crystal growth and oxidation of impurities andintermediates including FFCA. One of the functions of the secondaryoxidation zone is to convert FFCA to FDCA. FFCA is consideredmonofunctional relative to a polyester condensation reaction because itcontains only one carboxylic acid. FFCA is present in the crudecarboxylic acid composition stream. FFCA is generated in the primaryoxidation zone 100 because the reaction of 5-HMF to FFCA can be abouteight times faster than the reaction of FFCA to the desireddi-functional product FDCA. Additional air or molecular oxygen may befed to the secondary oxidation zone in an amount necessary to oxidize asubstantial portion of the partially oxidized products such as FFCA tothe corresponding carboxylic acid FDCA. Generally, at least 70% byweight, or at least 80 wt %, or at least 90 wt % of the FFCA present inthe crude carboxylic acid composition exiting the primary oxidation zonecan be converted to FDCA in the secondary oxidation zone. Significantconcentrations of monofunctional molecules like FFCA in the dried,purified FDCA product are particularly detrimental to polymerizationprocesses as they may act as chain terminators during the polyestercondensation reaction.

If a secondary oxidation zone is employed, the secondary oxidationslurry can be crystallized to form a crystallized slurry stream. Vaporfrom the crystallization zone can be condensed in at least one condenserand returned to the crystallization zone or recycled, or it can bewithdrawn or sent to an energy recovery device. The crystallizer off-gascan be removed and routed to a recovery system where the solvent isremoved, and crystallizer off gas containing VOC's may be treated, forexample, by incineration in a catalytic oxidation unit. The crystallizercan be operated by cooling the secondary oxidation slurry to atemperature between about 40° C. to about 175° C. to form a crystallizedslurry stream.

The crystallized slurry stream can then be subjected to a cooling zone200 if desired and the process continued as described above.

Instead of using a wet cake, one may produce a dried solid. The wet cakeproduced in the solid liquid separation zone 300 can be dried in adrying zone 400 to generate a dry purified carboxylic acid solid 410 anda vapor stream 420. The vapor stream 420 typically comprises the washsolvent vapor used in the solid liquid separation zone, and mayadditionally contain the solvent used in the primary oxidation zone. Thedrying zone 400 comprises at least one dryer and can be accomplished byany means known in the art that is capable of evaporating at least 10%of the volatiles remaining in the purified wet cake stream to producethe dried, purified carboxylic acid solids. For example, indirectcontact dryers include, but are not limited to, a rotary steam tubedryer, a Single Shaft Porcupine dryer, and a Bepex Solidaire dryer.Direct contact dryers include, but are not limited to, a fluid bed dryerand drying in a convey line.

The dried, purified carboxylic acid solids comprising purified FDCA canbe a carboxylic acid composition with less than 8% moisture, preferablyless than 5% moisture, and more preferably less than 1% moisture, andeven more preferably less than 0.5%, and yet more preferably less than0.1%.

A vacuum system can be utilized to draw vapor stream 420 from the dryingzone 400. If a vacuum system is used in this fashion, the pressure atthe dryer outlet can range from about 760 mmHg to about 400 mmHg, fromabout 760 mmHg to about 600 mmHg, from about 760 mmHg to about 700 mmHg,from about 760 mmHg to about 720 mmHg, and from about 760 mmHg to about740 mmHg wherein pressure is measured in mmHg above absolute vacuum.

The dried, purified carboxylic acid solids, or the solids in the wetcake, desirably have a b* less than about 9.0, or less than about 6.0,or less than about 5.0, or less than about 4.0. or less than about 3.

It should be appreciated that the process zones previously described canbe utilized in any other logical order to produce the dried, purifiedcarboxylic acid. It should also be appreciated that when the processzones are reordered that the process conditions may change. It is alsounderstood that all percent values are weight percents.

One function of drying zone 400 is to remove by evaporation oxidationsolvent comprising a mono-carboxylic acid with 2 to 6 carbons that canbe present in the crude carboxylic acid wet cake stream 310. The %moisture in crude carboxylic acid wet cake stream 310 typically rangesfrom 4.0% by weight to 30% by weight depending on the operationconditions of the solid-liquid separation zone 300. If for example, theliquid portion of stream 310 is about 90% acetic acid, the amount ofacetic acid present in stream 310 can range from about 3.6 weight % to27 weight %. It is desirable to remove acetic acid prior toesterification zone 500 because acetic acid will react with the alcoholpresent in the zone 500 to create unwanted by products. For example, ifmethanol is fed to esterification zone 500 for the purpose of reactingwith FDCA, it will also react with acetic acid present to form methylacetate and therefore consume methanol and generate an unwantedby-product. It is desirable to minimize the acetic acid content of thecrude carboxylic acid stream comprising FDCA that is fed toesterification zone 500 to less than 3.6 weight %, preferably less than1 weight %, and more preferably less than 0.5 weight %, and mostpreferably less than 0.1 weight %. One method for achieving this is todry a crude carboxylic acid wet cake stream 310 comprising acetic acidprior to routing the crude carboxylic to esterification zone 500.Another method for minimizing the oxidation solvent comprisingmono-carboxylic acid with carbons ranging from 2 to 5 in the crudecarboxylic acid stream 410 routed to esterification zone 500 to anacceptable level without utilizing a dryer zone 400 is to conductnon-monocarboxylic acid wash or washes in solid-liquid separation zone300 to wash the oxidation solvent from the solids with a wash comprisingany wash solvent compatible with the esterification zone 500 chemistryto generate a crude carboxylic acid wet cake stream 310 suitable forrouting directly to esterification zone 500 without being dried indrying zone 400. Acceptable wash solvents comprise solvents that do notmake undesirable by products in esterification zone 500. For example,water is an acceptable wash solvent to displace acetic acid from solidsin solid-liquid separation zone 300. Another acceptable wash solvent isan alcohol that will be used as a reactant in the esterification zone500. There can be multiple and separate washes in the solid liquidseparation zone 300. A wash feed can comprise water up to 100 weight %.A wash feed can comprise an alcohol up to 100 weight %. A wash feed cancomprise methanol up to 100%. A wash feed can comprise the same alcoholutilized in the esterification zone 500 for reaction with FDCA to formthe di-ester product. In one embodiment, a wet cake dewatering step canbe used after the wet cake is formed in the solid liquid separation zone300 and before any non-acetic acid wash is employed. This dewateringstep will minimize the liquid content of the wet cake prior to washingwith a non-acetic acid wash solvent such as water and or methanol asdescribed above, thus minimizing the cost to separate any mixtures ofacetic acid and non-acetic acid wash solvents that are generated insolid-liquid separation zone 300.

The solid dicarboxylic acid composition 410, which can be either driedcarboxylic acid solids or wet cake, comprising FDCA, and the alcoholcomposition stream 520 are fed to the esterification reaction zone 500.The solid dicarboxylic acid composition 410 can be shipped via truck,ship, or rail as solids. However, an advantage of the invention is thatthe process for the oxidation of the oxidizable material containing thefuran group can be integrated with the process for the manufacture ofthe crude diester composition.

An integrated process includes co-locating the two manufacturingfacilities, one for oxidation and the other for esterification, within10 miles, or within 5 miles, or within 2 miles, or within 1 mile, orwithin ½ mile of each other. An integrated process also includes havingthe two manufacturing facilities in solid or fluid communication witheach other. If a solid dicarboxylic acid composition is produced, thesolids can be conveyed by any suitable means, such as air or belt, tothe esterification facility. If a wet cake dicarboxylic acid compositionis produced, the wet cake can be moved by belt or pumped as a liquidslurry to the facility for esterification.

EXAMPLES

This invention can be further illustrated by the following examples ofembodiments thereof, although it will be understood that these examplesare included merely for the purposes of illustration and are notintended to limit the scope of the invention unless otherwisespecifically indicated.

Example 1

6.5 g of crude FFCA and 43.7 g of MeOH were mixed in a clean and dry 100mL autoclave at a molar ratio of methanol to FDCA of 30. The autoclavemixture was heated to 100° C. in a closed system and let the pressuredevelop. After 6 h at 100° C. the reaction mixture was cooled to roomtemperature. A liquid product was obtained. GC analysis of the liquidproduct showed the following composition: 14.05 wt % of DMFCA based onthe weight of reaction product, 1.33 wt % of MDMFC based on the weightof product, 79.53 wt % of methanol based on the weight of product, and2.26 wt % of water.

Example 2

Example 1 was repeated at 170° C. for 6 h. GC analysis of the liquidproduct showed the following composition: 2.81 wt % of DMFCA based onthe weight of reaction product, 14.79 wt % of MDMFC based on the weightof product, 78.91 wt % of methanol based on the weight of product, and3.36 wt % of water.

Example 3

Example 1 was repeated at 200° C. for 6 h. GC analysis of the liquidproduct showed the following composition: 0.81 wt % of DMFCA based onthe weight of reaction product, 16.19 wt % of MDMFC based on the weightof product, 74.08 wt % of methanol based on the weight of product, and4.15 wt % of water.

Gas Chromatographic Method

Process samples were analyzed using a Shimadzu gas chromatograph Model2010 (or equivalent) equipped with a split/heated injector (300° C.) anda flame ionization detector (300° C.). A capillary column (60 meter×0.32mm ID) coated with (6% cyanopropylphenyl)-methylpolysiloxane at 1.0 tmfilm thickness (such as DB-1301 or equivalent) was employed. Helium wasused as the carrier gas with an initial column head pressure of 29.5 psiand an initial column flow of 3.93 mL/minute while the carrier gaslinear velocity of 45 cm! second was maintained constant throughout theentire oven temperature program. The column temperature was programmedas follows: The initial oven temperature was set at 80° C. and was heldfor 6 minutes, the oven was ramped up to 150° C. at 4° C./minute and washeld at 150° C. for 0 minute, the oven was ramped up to 240° C. at 10°C./minute and was held at 240° C. for 5 minutes, then the oven wasramped up to 290° C. at 10° C./minute and was held at 290° C. for 17.5minutes (the total run time was 60 mins). 1.0-gl of the prepared samplesolution was injected with a split ratio of 40:1. EZ-Chrom Elitechromatography data system software was used for data acquisition anddata processing. The sample preparation was done by weighing 0.1 g(accurate to 0.1 mg) of sample in a GC vial and adding 200.0 μl ISTDsolution (1% by volume of decane in pyridine) and 1000 μl of BSTFA (N,O-bis(trimethylsilyl) trifluoroacetamide) with 1% TMSC1(trimethylchlorosilane) to the GC vial. The content was heated at 80° C.for 30 minutes to ensure complete derivatization. 1.0 μl of thisprepared sample solution was injected for GC analysis.

What I claim is:
 1. A dialkyl-furan-2,5-dicarboxylate (DAFD) compositioncomprising solid particles of DAFD, wherein said composition comprises:(i) at least 98 wt. % of DAFD; (ii) 5-(alkoxycarbonyl)furan-2-carboxylicacid (ACFC) that if present, is present in an amount of not more than1000 ppm, and (iii) alkyl-5-formylfuran-2-carboxylate (AFFC) that ifpresent, is present in an amount of not more than 1000 ppm, wherein (iv)5-(dialkoxymethyl)furan-2-carboxylic acid (DAFCA) is present in anamount of not more than 1000 ppm, and (v) alkyl5-(dialkoxymethyl)furan-2-carboxylate (ADAFC) is present in an amount ofnot more than 1000 ppm, and wherein the composition contains not morethan 0.5 wt. % of water.
 2. The DAFD composition of claim 1, whereinsaid composition comprises: (i) not more than 100 ppm of ACFC, (ii) notmore than 100 ppm of AFFC, (iii) not more than 10 ppm of furandicarboxylic acid (FDCA), (iv) not more than 100 ppm of DAFCA, and (v)not more than 100 ppm of ADAFC.
 3. A dimethyl furan-2,5-dicarboxylate(DMFD) composition comprising solid particles of DMFD, wherein saidcomposition comprises: (i) at least 98 wt. % of DMFD; (ii)5-(methoxycarbonyl)furan-2-carboxylic acid (MCFC) that if present, ispresent in an amount of not more than 1000 ppm, and (iii)methyl-5-formylfuran-2-carboxylate (MFFC) that if present, is present inan amount of not more than 1000 ppm, wherein (iv)5-(dimethoxymethyl)furan-2-carboxylic acid (DMFCA) is present in anamount of not more than 1000 ppm, and (v) methyl5-(dimethoxymethyl)furan-2-carboxylate (MDMFC) is present in an amountof not more than 1000 ppm, and wherein the composition contains not morethan 0.5 wt. % water.
 4. The composition of claim 1, which contains lessthan 1000 ppm of furan dicarboxylic acid.
 5. The composition of claim 3,which contains less than 1000 ppm of furan dicarboxylic acid.